While the PWM IP in the Allwinner H6 SoC is fully compatible to those
used in older SoCs (H3, A64), it features a dedicated reset line which
needs to be de-asserted.
Add support for an optional "resets" DT property in our pwm-sun4i probe
routine, and assert and de-assert the reset line, where needed.
This allows to enable PWM support on the H6.